How can I test whether my camera’s built-in light meter is off?

A practical check is to compare your camera’s meter against a known reference.

• Use a handheld light meter if you have access to one. Meter the same scene with both devices under the same light and compare the suggested exposure.
• Try a simple histogram test: photograph an evenly lit, low-detail subject (slightly defocusing can help reduce detail). If exposure is correct, the histogram should cluster around the middle or slightly left of center for a neutral subject. If it consistently shifts about a stop to the right, that suggests overexposure.
• Use the Sunny 16 rule outdoors: in bright midday sun, a midtone subject should be exposed at about f/16 and shutter speed = 1/ISO. For ISO 100, that’s around 1/100 s at f/16 (or close, such as 1/125 s). If your camera meter gives a meaningfully different result under those conditions, it may be off.
• If you want a definitive answer, have the camera serviced/tested. A service center can check metering calibration with proper equipment.

Keep in mind that scene brightness, subject tone, and metering mode can affect results, so test with consistent, neutral subjects and stable lighting.